Fiber optic local area networks are typically implemented in a ring configuration. Such a network comprises a plurality of nodes arranged in a ring, the nodes being interconnected by optical fibers.
To transmit information from an originating node to a destination node, the data is transmitted from the originating node along the ring from one intervening node to the next until the destination node is reached. Illustratively, information arrives at a node via an incoming optical fiber. The incoming optical fiber is coupled to a receiver which converts the incoming information signal from optical to electrical form. Information leaves a node via an optical transmitter which converts a signal from electrical to optical form, the optical signal being transmitted out from the node via an outgoing optical fiber.
One problem with a fiber optic local area network having a ring configuration is that if one node fails the entire network or a significant portion thereof will be nonusable as no information can pass through a failed node. Accordingly, it is an object of the present invention to provide a reversible optical switch which in one state couples a node into a ring like optical network and which in a second state allows a node to be bypassed so that the network can continue to function in the event of a node failure.
In the event of a node failure or suspected node failure, it is desirable for a node to be tested by enabling the transmitter in the node to communicate via an optical path with the receiver in the node. Accordingly, it is a further object of the invention to provide a switch which, in a first state, couples a node into a ring like fiber optic network and which, in a second state, allows the node to be bypassed by the network, while simultaneously optically coupling the node transmitter to the node receiver to permit testing of the bypassed node.
In present implementations, the transmitter and receiver portions of a node are combined to form a single transceiver unit. The transceiver unit is connected to an interconnect housing by way of a duplex connector which enters the interconnect housing at one side thereof. The incoming and outgoing fibers are illustratively terminated in separate simplex connectors which enter the interconnect housing on a side opposite to that of the duplex connector of the transceiver. Accordingly, it is a further object of the present invention to provide a reversible optical switch coupled to the interconnect housing which, in a first state, provides substantially straight throughgoing optical paths to enable the incoming fiber to be coupled to the node receiver and the outgoing fiber to be coupled to the node transmitter. In a second state, the switch should provide a first "loop back" optical path that couples the incoming and outgoing fibers so that the transceiver is bypassed by the network and a second "loop back" optical path that couples the transmitter and receiver so that the bypassed node can be tested.